Such systems are known to generally present one or two molds, each comprising top and bottom mold halves defining an annular chamber for a green tire. The top mold half is usually connected to a moving crosspiece on the press, whereas the bottom mold half is mounted on the bed of the press and supports a deformable inner tube or curing bladder designed to occupy the said annular chamber when inflated with a heat-exchanging curing medium or media. The said curing media, usually consisting of relatively hot steam, is supplied under pressure by a external feeder, which provides for heating the curing media, possibly after producing and filtering it, and circulating it under pressure inside the mold for the length of time required for curing.
A major drawback of known systems of the aforementioned type is that they involve relatively high manufacturing cost and provide for relatively low output. Such systems in fact require a relatively high-cost press for every one or two molds, which press remains engaged throughout the entire curing operation.
Furthermore, the slightest change in design entails relatively prolonged downtime for machining, during which time the press remains idle. Also, if the heat-exchanging curing media employed consists, as it does in all known present cases, of relatively hot steam, systems of the aforementioned type must therefore include an extremely high-cost accessory system for water purification and steam production.
For partially overcoming these drawbacks, systems have been devised comprising a number of molds mounted in a fixed manner on an indexing fixture which, turning about a fixed vertical axis, feeds the molds, one by one, through a loading station where each mold is opened, loaded and closed by a fastening device on the mold itself. Each mold is then turned on the indexing fixture and supplied, as long as required for curing, with steam under pressure fed from a centralized feeding device connected to all the molds on the indexing fixture.
Though systems of the aforementioned type involve no presses and provide for using a large number of molds at the same time, they are nevertheless extremely expensive in that they also require a separate system for filtering, producing, heating and supplying steam, as well as a number of sliding joints for connecting each moving mold to the said system. Furthermore, the said indexing fixture, to which the bottom half of each mold is necessarily integrally connected, imposes the same supply route and the same curing time for each mold, with no possibility of selective curing.
Finally, in this case also, the slightest change in design entails relatively prolonged downtime during which the system remains idle.